Software Engineer

Xsolla

4d•Remote

About The Position

Xsolla is hiring a senior full-stack Software Engineer, Web3, for Xsolla ZK, its Web3 ecosystem on a zkSync-based Layer 2. The ecosystem includes smart wallets built on account abstraction, SDKs for game studios and partners, backend infrastructure for tokenizing in-game items and currencies, and decentralized applications including a DEX, NFT marketplace, and auction. The engineer will own product features end to end across backend, frontend, and production operations. They will make and document architectural decisions about how on-chain and off-chain components work together, and be responsible for the security and correctness of systems involving signing flows, user assets, keys, and secrets. The role participates in the team's production on-call rotation. The position builds backend services in Go and TypeScript, dApp frontends in React, smart-wallet integrations, and SDKs for external developers. It also involves monitoring production services and contracts, reviewing code, and configuring and maintaining AI coding tools in the team's repositories. The role is remote worldwide and full-time. The stated schedule is 10:00–19:00, flexible. The employment agreement is arranged through an entity or EOR according to the candidate's location. The engineer will work with product managers, designers, smart-contract, backend and frontend engineers, QA, and DevOps.

Requirements

At least 5 years of commercial software development experience, with senior-level production experience across backend and frontend.
Experience shipping dApps to production and maintaining them.
Production experience with Web3 libraries and wallets, including viem and wagmi: clients and transports, contract reads and writes with typed ABIs, event subscriptions, wagmi hooks and connectors, and caching and invalidation of on-chain state.
Understanding of wallet signers, including EOAs, browser and embedded wallets, smart accounts, personal_sign (EIP-191), typed data (EIP-712), the EIP-1193 provider, and network switching.
Hands-on experience with smart wallets, including UserOperations, gas sponsorship through paymasters, and signature validation for contract accounts (ERC-1271).
Production service development experience with Go and TypeScript (Node.js).
Experience processing on-chain events, including idempotency, reorg handling, and retries.
Experience with asynchronous messaging and event-driven design using Kafka, RabbitMQ, or NATS, including delivery guarantees, ordering, and reprocessing.
Experience with PostgreSQL and Redis.
Experience designing REST and gRPC APIs, including versioning and backward compatibility.
Experience with React and TypeScript, including the rendering model, state management, and performance.
Knowledge of web security fundamentals, including XSS, CSRF, CSP, and safe handling of signatures and keys in the browser.
Ability to read and understand Solidity contracts and the EVM—including storage, gas, call semantics, proxy upgrade patterns, and access control—to integrate safely and review changes.
Understanding of common contract vulnerabilities, including reentrancy, front-running/MEV, oracle manipulation, and signature replay, and their off-chain effects.
Experience with Docker and Kubernetes sufficient to deploy and debug one's own services.
Experience with observability, including metrics, logs, tracing, and alerting for services and contracts, and diagnosing production incidents. Datadog is used; Prometheus, Grafana, ELK/Graylog, or OpenTelemetry experience also counts.
Experience with unit, integration, and E2E testing.
Experience with Git and CI/CD, using GitLab CI or similar.
Daily hands-on use of AI coding tools such as Claude Code, Codex, or Cursor for development and review, including configuring them for a repository.
Spoken English at B2 level or higher.

Nice To Haves

Experience with zkSync/ZK Stack and zk-rollup specifics.
Experience designing, writing, and testing Solidity smart contracts with Foundry and deploying and upgrading them safely.
Experience building ERC-4337 infrastructure, including bundlers and paymasters; knowledge of EIP-6963 and EIP-5792.
Knowledge of DeFi, including DEX and AMM mechanics.
Knowledge of NFTs and marketplaces, including ERC-721, ERC-1155, and auction mechanics.
Experience with Layer 2 infrastructure, including running nodes, indexers, and bridges.
Experience designing SDKs for external developers.
Gaming domain experience.

Responsibilities

Own features end to end, spanning backend, frontend, and production.
Design and document the on-chain/off-chain architecture of products, deciding what belongs in smart contracts versus services and how the components remain consistent.
Ensure the security and correctness of shipped systems, including signing flows and interactions with contracts that hold user assets, keys, and secrets.
Operate production services and participate in the team's on-call rotation.
Build backend services in Go and TypeScript for chain indexing, transaction relaying, event processing, and APIs for dApps and SDKs.
Build backend infrastructure for tokenizing in-game items and currencies.
Build React dApp frontends, including wallet connection, transaction signing, and displaying on-chain state.
Integrate smart wallets into products, including accounts, paymasters, and bundlers.
Develop SDKs used by game studios and partners.
Monitor services and contracts in production and participate in on-call.
Review code.
Set up and maintain AI tooling in repositories, including rules, context, and harnesses for Claude Code, Codex, and Cursor.